The present invention relates to a new and improved construction of a calender or rolling mill.
In its more particular aspects, the present invention relates to a new and improved construction of a calender or rolling mill comprising a predetermined number of rolls which are moveable in at least one pressing direction. At least one of the rolls is structured as a tubular roll or controlled deflection roll comprising a stationary roll support member or beam and a roll shell which is rotatable about the stationary roll support member and which is displaceable in radial direction over its entire length. The roll shell is supported at the roll support member or beam by means of pressure or support elements which are supplied with pressure fluid and exert a supporting force on the roll shell. At least one position sensor is provided in order to determine the position of at least one of the rolls and there are also provided regulating means for regulating the position of the rolls.
In calendars of the type as known, for example, from U.S. Pat. No. 4,357,743, granted Nov. 9, 1982 or British Patent Publication No. 2,091,150, published July 28, 1982 and the cognate U.S. Pat. No. 4,472,958, granted Sept. 25, 1984, the lowest, and if desired, also the topmost roll constitutes a tubular roll or controlled deflection roll of the type as described, for example, in U.S. Pat. No. 3,885,283, granted May 27, 1975.
The tubular roll or controlled deflection roll is constructed to include a roll shell which is displaceable relative to the roll support member or beam in vertical direction, i.e. in the pressure or pressing plane. The entire roll arrangement or roll bank, therefore, would float with respect to the pressing direction with the consequence that the position of the roll nips or gaps would be undefined even if all forces are balanced. In order to establish the desired and required position of the rolls, and thus, of the roll nips or gaps, there are therefore provided position sensors which determine the position of the roll shell at its ends relative to the roll support member or beam or relative to a roll carrying frame. The position sensors control regulating means which regulate the pressure of the pressure fluid for the pressure elements such that the roll shell and thus also the roll nips or gaps assume the intended position. When a related position sensor is arranged on both sides or at both ends of the roll shell, there can be simultaneously maintained a predetermined position of the rolls by a differential regulation.
Calenders of this type are used, for example, for manufacturing foils of metal, paper or plastic foils or sheets or in the manufacture of textile goods. In such applications, the web of the material which is to be smoothed or calendered, rolled or processed, sequentially passes through the roll nips or gaps formed between individual ones of the rolls. As described, for example, in U.S. Pat. No. 3,884,141, granted May 20, 1975, such calender and the roll nips or gaps therein are opened in such a manner that the regulating means for regulating the pressure of the pressure fluid for the pressure or support elements are readjusted or reset so that the individual rolls are lowered to bear upon related stops. These individual stops or abutments are selected such that an open gap is formed between the entire number of rolls. After the introduction of the web of material or after exchange of one of the rolls, the regulating means are re-activated and the entire roll arrangement is brought again into the intended position, whereby the roll nips or gaps are again closed.
In such known calenders and roll arrangements, it is merely intended that the regulating means regulate the roll position with respect to a predetermined positional value and during the regulating operation there is always effective the entire roll arrangement and its total weight. In practice, however, there is a desire for greater flexibility in the use of the calender, that is, one and the same calender should be able to operate upon different types of materials and should be able to perform different processing operations without complicated reconstructions. It would be necessary therefor to selectively use either all of the rolls in the calender or only part of the rolls contained therein. Consequently, the number of effective or operative rolls should be selectable as a function of the material to be processed. Furthermore, it would be desirable to provide a compensation for changes in the diameter of the rolls, for example, due to abrasive or grinding wear during the service life of the rolls. The known calenders or roll arrangements of the initially mentioned type possessing the advantage of using controlled deflection rolls, however, could not heretofore satisfy such requirements or only when associated with a great additional expense.